Abstract

We present simultaneous high time resolution (1–10 Hz) X‐ray and optical observations of the persistent LMXBs Sco X‐1 and V801 Ara( = 4U 1636‐536). In the case of Sco X‐1 we find that the Bowen∕HeII emission lags the X‐ray light‐curves with a light travel time of ∼ 11–16 s which is consistent with reprocessing in the donor star. We also present the detection of three correlated X‐ray∕optical bursts in V801 ara. Although this latter project is still in progress our preliminary results obtained by subtracting the Continuum light‐curve from the Bowen∕HeII data provide evidence of orbital phase dependent echoes from the companion star.